Field of the invention
[0001] The present invention relates to a cooling device for gas analysis of combustion
gases, normally used in industrial plants.
[0002] In particular, the invention can be used in all combustion plants as well as in case
of internal combustion engines.
Background of the invention
[0003] As well known, in certain industrial fields, where exhaust gases are produced that
are generated by combustion, special rules are applied for controlling and monitoring
the concentration of pollutants present in such gases.
[0004] Then, a dedicate equipment is necessary for exhaust gas analysis at the exit of a
chimney or of an endothermic engine, in order to monitor the level of the pollutant
and to warn when dangerous thresholds are exceeded.
[0005] However, in the exhaust gas coming from industrial burners or engines a high ratio
of water vapour is present that influences strongly the operations of calibrating
and setting the analysis equipment, as well as the operations of detecting the pollutants,
such as, for example CO, CO
2 or others.
[0006] To this end, a system is used for reducing and keeping fixed the content of water
vapour and of other condensable components of the gas. In particular this system provides
having a gas cooling plant that allows their dehydration before the analysis. In particular
the vapour and the other condensable components of the gas that can affect the measurement
are retained in a refrigerator, leaving the dry gas to pass.
[0007] The known cooling devices for this purpose comprise, generally, a heat exchanger
where heat is exchanged from the gas towards a cooling fluid. In particular a cooling
circuit is provided comprising a compressor, a forced ventilation condenser and an
evaporator. The circuit is sealed hermetically and filled of cooling fluid.
[0008] Such plants require, for their features, a lot of handwork for maintenance of the
compressor and other movable parts, as well as a periodic change of the cooling fluid.
[0009] A further drawback is a difficulty in adjusting quickly the cooling circuit concerning
temperature and flow rate of the cooling fluid, in order to adjust the cooling power
and, then, the amount of water vapour removed. In particular, a change of cooling
power is desirable when the type or the flow rate changes of the gas to analyse.
[0010] Furthermore, the known systems are stiff and not adapted to a flexible or intermittent
use, since they need to achieve a steady condition for a correct operation, with subsequent
high power consumption and wear owing to their cyclical use.
[0011] In addition, in industrial plants and in workshops, for safety reasons, there is
often lack of electric energy socks, and the known types of mobile gas analysers with
coolant circuit would require not much practical and risky electric connections.
[0012] Finally, such cooling systems are bulky, and then are heavy for a portable use, when
the measuring instrument has to be moved to different sites.
Summary of the invention
[0013] It is therefore a feature of the present invention to provide a gas analyser with
cooling device with a coolant fluid flow variable in flow rate and temperature.
[0014] It is also a feature of the present invention to provide a gas analyser with cooling
device structurally easy and implemented an each industrial plant of analysis of the
gas.
[0015] It is another feature of the present invention to provide a gas analyser with cooling
device that does not require periodic maintenance operations.
[0016] It is also a feature of the present invention to provide a gas analyser with cooling
device that is of minimum encumbrance.
[0017] It is a further feature of the present invention to provide a gas analyser with cooling
device with a minimum energy consumption.
[0018] It is finally a feature of the present invention to provide a gas analyser with a
cooling device that does not require an electric supply.
[0019] These and other objects are achieved by a gas analyser comprising:
- a gas analysis unit having an inlet port for a gas to analyse;
- a filter having an inlet duct for the gas, with a determined rate of humidity, and
an outlet duct of a gas with reduced values of water vapour, said outlet duct communicating
with said inlet port of the gas analysis unit,
- wherein said filter comprises a heat exchanger adapted to cool said gas as input and
to reduce its rate of humidity by means of condensation,
characterised in that it comprises furthermore,
- a fastening member for a source of compressed fluid at room temperature, in particular
compressed air,
- a cooling device for said compressed fluid fed through said fastening member, wherein
said cooling device provides an expansion zone for said compressed fluid that causes
said fluid to cool,
- an exit port from said cooling device for feeding to said heat exchanger said cooled
fluid and cooling said gas when entering the apparatus causing condensed humidity
of the vapour in it present.
[0020] Advantageously, said cooling device comprises a duct having a conditioning zone where
a separation of said compressed fluid is obtained respectively into a current of warm
fluid and into a cold fluid current, said cold fluid current being directed towards
said exit port for feeding said heat exchanger. In particular said duct comprises,
furthermore, a discharging into the environment said warm fluid current.
[0021] In particular, the fluid such as compressed air is driven into the duct in a central
zone thereof, cause a vortical motion of the air at a high speed by means of tangential
nozzles. This vortical motion extends along the duct reaching a discharge zone of
the warm air, where a part of it is evacuated through said bleed valve. The remaining
air continues to rotate in the duct and is caused to follow an opposite direction
making a second vortical motion in the area of low pressure that is caused to the
centre of the first vortical motion. The second vortical motion proceeds at a lower
speed and the heat freed by the kinetic energy remains in the first vortical motion,
such that a cold air flow exits in an opposite direction with respect to the warm
air bleed valve.
[0022] Preferably, said cold fluid current is adjustable in flow rate and in temperature
responsive to the compressed fluid input pressure.
[0023] Advantageously, said cold air outgoing from said exchanger is recirculated in a plant
to generate compressed air.
[0024] Alternatively, said cold air outgoing from said exchanger is dispersed into the environment.
[0025] Advantageously, said filter has a container for collecting condensed humidity, and
a corresponding discharge valve.
[0026] According to another aspect of the invention, a method for reducing the content of
humidity of a gas that enters a gas analyser comprises the steps of:
- introducing in a filtering chamber the gas containing gas components to analyse, and
cooling said gas by a heat exchanger at a temperature set between 1 and 15°C, said
heat exchanger being flown through by a cold fluid coming from a cooling device;
- introducing said fluid, such as compressed air, into a duct of said cooling device;
- cooling said compressed air by an expansion of said air in said duct;
- feeding said exchanger with said cooled air.
[0027] Advantageously, said cooling step comprises the further steps of:
- forming a first vortical motion of the air that extends along a first direction along
said duct;
- creating a depression zone at the centre of said first vortical motion;
- discharging into the environment a first part of the compressed air that follows said
first vortical motion;
- forming in said depression zone a second vortical motion of a second part of the air,
which has remained in said duct, said second vortical motion being co-axial to said
first vortical motion and proceeding in an opposite direction with respect to said
first direction,
- reaching by said second part of the air an expansion zone;
- expanding said air in said ezpansion zone and forming said cooled air.
[0028] In particular, said second part of the air proceeds in said opposite direction, at
a lower speed, such that the heat freed by the kinetic energy remains in said first
vortical motion.
Brief description of the drawings
[0029] Further characteristic and advantages of the gas analyser with dehydration device,
according to the invention, will be made clearer with the following description of
an exemplary embodiment thereof, exemplifying but not limitative, with reference to
the attached drawings, in which like reference characters designed the same or similar
parts, throughout the figures of which:
- Fig. 1 shows diagrammatically a block diagram that identifies the steps that start
from picking up the gas at the exit of a combustion plant and end with the analysis
procedure;
- Fig. 2 shows diagrammatically the path of the compressed air in the cooling device
and in the heat exchanger, with relative condensation of the vapours;
- Figs. 3 and 4 show a cross sectional view of a cooling filter, according to the invention;
- Fig. 5 shows a diagrammatical view of the operation of the cooling device outlining
the flow of the gas and of the cooling fluid along with the electric parts.
Description of a preferred exemplary embodiment.
[0030] With reference to Fig. 1, in the block diagram the path is shown of the gas in order
to analyse the polluting components in an industrial plant where combustion occurs.
In particular, Fig. 1 shows a combustion plant 1 from which a sample of the gas 2
that exits from the chimney is spilled and reaches a cooling device 3 where, before
reaching a gas analyser 4, a cooling of the gas occurs which, by condensing the gas
humidity, reduces the ratio of water vapour present in the gas. The main reason of
the dehydration is because the instruments of analysis, such as, for example, infrared
sensors that allow to detect pollutants in the gas, are influenced by water molecules
present in the gas, thus affecting the measurement of the pollutants.
[0031] The operation of an infrared analyser provides emission of broadband waves by a source.
For each measured gas, the waves is carried out pass alternatively, through a measurement
chamber at one end of which an interferential optical narrowband filter (infrared)
for the gas to measure is mounted. In said cell, at a determined pressure, the gas
to examine is inserted.
[0032] A suitable optical system directs the infrared waves into the measurement chamber
and then to a detector that receives and amplifies alternatively the two signals,
one of which is a reference signal and the other a measurement signal. The concentration
of the gas is correlated monotonically to the difference between the two signals.
Possible interfering agents contained in the sample, such as a high concentration
of water vapour, would negatively affect the measurement.
[0033] In Fig. 2 the diagrammatical view of a conditioning unit of a gas analyser, according
to the invention, comprises an gas analysing unit 4 (visible in Fig. 1) with an inlet
port for a gas to analyse and a filter 3 with an inlet duct 5 for a gas 10, which
has a determined rate of humidity, and an outlet duct 6 of a gas 10' with reduced
values of water vapour. Furthermore, the outlet duct 6 communicates with the inlet
of the gas analysing unit 4 in Fig. 1.
[0034] In particular, the filter 3 provides a heat exchanger 7 adapted to cool the gas 10
and to reduce its rate of humidity by condensation.
[0035] The structure of the filter 3 comprises, furthermore, a fastening portion 9 for a
source of compressed fluid 11 at room temperature, in particular compressed air, a
cooling device 12 of the compressed fluid 11 fed through the fastening portion 9 and
an exit port 19 for exiting from the cooling device 12 and feeding a cooled fluid
into heat exchanger 7, which cools the gas 10 causing humidity to condense.
[0036] Operatively, the cooling device 12 comprises a duct 15 with a conditioning zone 14,
where a separation of the compressed fluid 11 is obtained, respectively into a warm
fluid current 16 and into a cold fluid current 17. The cold fluid current 17 is directed
towards exit mouth 19 for feeding the heat exchanger 4. In particular duct 15 comprises,
furthermore, a bleed valve 20 for discharging into the environment the current of
warm fluid 16.
[0037] In detail, the fluid 11, such as compressed air, is driven into the duct 15 in a
central zone 14 thereof, causing a vortical motion of the air at a high speed by means
of tangential nozzles (not shown). This vortical motion extends along the duct 15
reaching a discharge zone of the air, where the warmest part of it is evacuated through
bleed valve 20. The remaining air continues to rotate in the duct 15 and is caused
to follow an opposite direction proceeds according to a second vortical motion in
the area of low pressure, which is created at the centre of the first vortical motion.
The second vortical motion proceeds at a lower speed and the heat freed by the kinetic
energy remains in the first vortical motion, such that in an opposite direction with
respect to bleed valve 20 of the warmer air, a colder air flow 17 exits. In particular
the cooling device 12 provides an expansion zone 13 of the compressed fluid 11 that
causes the air to cool.
[0038] The cold air flow 17 crosses the heat exchanger 7 and causes the gas 10 to cool in
the filter 4, from which condensed humidity 10'' is separates leaving the gas to analyse
10' to pass without a substantial content of humidity. Condensed humidity 10" is collected
on the bottom of the same filter 4 and eliminated through a tap 22 whereas the cold
air flow, which has adsorbed heat from the gas, comes to an outlet mouth 21, where
it can be dispersed into the environment, or that can be recovered and used again
if it still has a temperature lower than the environment.
[0039] The present exemplary embodiment allows to adjust the flow rate of the cold fluid
current 17 and also to adjust its temperature responsive to the pressure of the compressed
fluid 11;
[0040] Fig. 3 shows a cross sectional view of filter 4, according to the invention. As previously
described it comprises a heat exchanger 7 that cools a gas 10 coming from a duct 5,
with a measured ratio of water vapour, and causes condensed humidity to be collected
in a container 25. The cold air flow 17 present in exchanger 7 is obtained by cooling
device 12, visible in Fig. 4 according to an elevational side view of filter 4. One
of the main advantages of such a filter is a reduced size of encumbrance, and this
is advantageous in many fields, for example, portable analysers for workshops where
the emissions in the engines are measured.
[0041] Fig. 5 shows a connection of the circuit of dehydration that comprises filter 4 connected
directly with cooling device 12 and a thermocouple 37 that controls, by a temperature
regulator 35, the cold current flow 17 that runs through heat exchanger 7 (visible
in Fig. 2). The gas 10', at the exit of duct 6 of filter 4, has a reduced ratio of
water vapour, and is sent to the analyser (not shown).
[0042] In particular, the compressed air flow 11 before being inserted at a determined pressure
in cooling device 12 passes through a condense separator 34 and an air separator 32,
in order o recover cold air 17 (visible in Fig. 2) exiting from exchanger 7. The flow
rate of compressed fluid 11 is adjusted by a solenoid valve 33, connected in turn
with the temperature regulator 35. This way, according to the flow rate and to the
temperature of flow 11, running through duct 9 of device 12, it is possible to adjust
the cooling power of the exchanger 7 (visible in Fig. 2). This solution allows a high
flexibility of analysis since, according to the rate of humidity present cheap and
suitably adjustable dehydration systems can be modulated. Furthermore, in the diagrammatical
view of Fig. 5, a filter 31 at the outlet of a fitting 22 is present, for emptying
the condensed humidity and collecting the humidity in container 25, and a pump 30
for unloading the same.
[0043] The foregoing description of a specific embodiment will so fully reveal the invention
according to the conceptual point of view, so that others, by applying current knowledge,
will be able to modify and/or adapt for various applications such an embodiment without
further research and without parting from the invention, and it is therefore to be
understood that such adaptations and modifications will have to be considered as equivalent
to the specific embodiment. The means and the materials to realise the different functions
described herein could have a different nature without, for this reason, departing
from the field of the invention. It is to be understood that the phraseology or terminology
employed herein is for the purpose of description and not of limitation.
1. An analyser comprising:
- a gas analysis unit having an inlet port for a gas to analyse;
- a filter having an inlet duct for a gas, with a determined rate of humidity, and
an outlet duct of a gas with reduced values of water vapour, said outlet duct communicating
with said inlet of said gas analysis unit,
- wherein said filter comprises a heat exchanger adapted to cool said gas and to reduce
its rate of humidity by condensation,
characterised in that it comprises furthermore,
- a fastening member for connecting a source of compressed fluid at room temperature,
in particular compressed air,
- a cooling device for said compressed fluid fed through said fastening member, wherein
said cooling device provides an expansion zone for said compressed fluid that causes
said fluid to cool,
- an exit port from said cooling device for feeding said cooled fluid to said heat
exchanger and cooling said gas when entering the apparatus causing condensation of
the vapour in it present.
2. An analyser, according to claim 1, wherein said cooling device comprises a duct having
a conditioning zone where a separation of said compressed fluid is obtained respectively
into a warm fluid current and into a cold fluid current, said cold fluid current being
directed towards said exit port for feeding said heat exchanger.
3. An analyser, according to claim 2, wherein said duct comprises, furthermore, a vent
for discharging into the environment said warm fluid current.
4. An analyser, according to claim 2, wherein said cold fluid current is adjustable in
flow rate and in temperature responsive to the compressed fluid input pressure.
5. An analyser, according to claim 2, wherein said duct comprises nozzles arranged tangentially
for causing a vortical motion to said compressed which enters said cooling device.
6. An analyser, according to claim 2, wherein said duct comprises an expansion zone for
a part of the compressed air that is not discharged from said bleed valve.
7. An analyser, according to claim 1, wherein means are provided for adjusting the flow
rate of compressed fluid entering said cooling device.
8. A method for reducing the content of humidity of a gas that enters a gas analyser
comprising the steps of:
- introducing in a filtering chamber the gas containing gas components to analyse,
and cooling said gas by a heat exchanger at a temperature set between 1 and 15°C,
said heat exchanger being flown through by a cold fluid coming from a cooling device;
- introducing said fluid, such as compressed air, into a duct of said cooling device;
- cooling said compressed air by an expansion of said air in said duct;
- feeding said exchanger with said cooled air.
9. Method according to claim 8, wherein said cooling step comprises the further steps
of:
- forming a first vortical motion of the air that extends along a first direction
along said duct;
- creating a depression zone at the centre of said first vortical motion;
- discharging into the environment a first part of the compressed air that follows
said first vortical motion;
- forming in said depression zone a second vortical motion of a second part of the
air, which has remained in said duct, said second vortical motion being co-axial to
said first vortical motion and proceeding in an opposite direction with respect to
said first direction,
- reaching by said second part of the air an expansion zone;
- expansion of said second part of the air making said cooled air;
10. Method according to claim 9, wherein said second part of the air proceeds in said
opposite direction, at a lower speed, such that the heat freed by the kinetic energy
remains in said first vortical motion.